The present invention relates generally to solenoid-operated valve devices for controlling industrial process systems, and more particularly to a system that allows for a continuous flow of industrial process gas through a valve while the solenoid controlling the valve is experiencing down time.
Modern process or manufacturing plants contain innumerable operating components. These components are tied together to form systems controlled by instrumentation and control systems containing sensors and controllers. The instrumentation and control systems on such plants not only serve to control the functions of the various components in order to achieve the desired process conditions, but they also provide the facility to safely modify or discontinue the operation of all or a portion of the plant's systems in order to avoid an unsafe situation or condition.
For example, in a semiconductor manufacturing plant, gases/chemicals are handled by gas delivery equipment consisting of numerous valves and pressure sensors, with each delivery system controlled by a dedicated process control system (controller). The process delivery equipment supplies gas/chemical to a process tool where wafer fabrication is conducted through pneumatically operated valves. Such valves are operated by pneumatic actuators connected through solenoid operated pilot valves to the pneumatic control source.
In operation, the solenoid-operated valves of such systems serve to initiate a process whereby a fluid or pneumatic supply is either applied to or vented from the process valve actuator when one or more operatively associated solenoid-operated valves changes state or position in a predetermined manner, e.g., when the solenoid-operated valve is de-energized by the controller.
It takes a variety of different process tools and many processes steps involving the delivery of a variety of gases to ultimately create a semiconductor device layer-by-layer on a silicon wafer. As this process can take several days or weeks, depending on the complexity of the semiconductor device, the process tools preferably operate 24/7. This requires the gas delivery equipment supporting the process tools to supply a constant, uninterrupted flow of gas or chemical. An unscheduled interruption of a gas/chemical at the tool could result in a failed process step which may render useless the silicon wafers in-process at the time. The monetary value of this loss of silicon wafers can be significant, often listed in millions of dollars of lost revenue.
Thus, there exists a need for an apparatus and method to ensure a continuous flow of pressurized gas to the pneumatic valves in manufacturing processes when the contolling solenoid valves are de-energized for any reason, including failure and maintenance.